Ultrathin Li metal anode with a thickness of <30 μm in combination with state-of-art cathodes could promise high-energy lithium metal batteries (LMBs). Here, we report a facile spin steaming technology to design the topological structures of Ti3C2Tx MXene film as Li host by mixing a trace of cellulose nanofiber (CNF). The interlocked topological microstructure between MXene sheets and microspheres-forming assisted by CNF contributes greatly to enhanced mechanical strength and flexibility of the resultant MXene@CNF film. More importantly, the MXene sheets with abundant Li nucleation sites shows a desirable affinity for Li. As a result, a flexible, ultrathin (~25 μm), and self-supporting MXene@CNF/Li composite anode without rampant Li dendrites, and with favorable cycling stability with high real capacity of Li is realized. The as-obtained hybrid Li anode matches with flexible self-supporting LiFePO4/cellulose nanofiber (LFP@CNF) cathodes to construct fully flexible LMBs with high specific capacity and outstanding stability.